1. Field of the Invention
This invention relates generally to medical appliances; and more particularly to a device for inserting into a patient's body a medical appliance such as a cannula, e.g. an intravascular cannula, or such as a guidewire used for emplacing catheters etc. The invention is for helping protect people from contracting diseases (particularly fatal diseases such as AIDS and hepatitis) through accidental puncture by needles that have been used in diseased patients.
2. Prior Art
U.S. Pat. No. 4,747,831 to Kulli sets forth the state of the pertinent art and is, in its entirety, incorporated herein by reference. Kulli teaches a safety device for use in inserting a cannula into a patient and for thereafter protecting people from contact with portions of the device that have been within the patient.
(For purposes of this document as in the Kulli patent, the term "cannula" means a catheter assembly consisting of primarily a hub and short tube--as pictured and described in the Kulli patent [column 3, lines 25 through 37] and herein. As already mentioned the technology is not necessarily limited to use with cannulae directly but is useful as well in insertion of other medical appliances such as catheter guidewires.)
Kulli's device includes a needle for piercing a patient and for guiding and carrying a cannula or other appliance into place within such a patient; the needle has a shaft with at least one sharp end. His device also includes a hollow handle adapted to enclose at least the sharp end of the needle beyond reach of people's fingers.
In one major facet or aspect of preferred embodiments of Kulli's invention, the invention also includes some means (denominated the "securing means") for securing the shaft to the handle, with the sharp end projecting from the handle. It also includes some means (the "releasing means") for releasing the securing means and for substantially permanently retracting the sharp end of the needle into the handle and beyond reach of people's fingers. The releasing and retracting means are manually actuable by a simple unitary motion, of amplitude that is substantially shorter than the shaft of the needle.
In a second major aspect or facet, Kulli's invention also includes (in addition to the needle and hollow handle) a block fixed to and extending from the needle. The block is restrained within the handle with the sharp end of the needle projecting out of the handle through the aperture, and adapted for motion within the handle to withdraw the needle into the handle. The invention in this second major aspect further includes a trigger mechanism, which is actuable from outside the handle for releasing the block. The trigger mechanism also includes positive biasing means for forcibly moving the block within the handle to substantially permanently retract the sharp end of the needle into the handle and beyond reach of people's fingers.
Many other details of the Kulli invention are discussed at length in his '831 patent and for economy's sake will not be repeated directly here, though as already noted they are all incorporated into this document by reference.
In the course of very extensive efforts directed toward preparation of the Kulli invention for the marketplace, it has been confirmed that his invention is entirely operational and serviceable for all the purposes described. No criticism of the structure or function of Kulli's invention is intended by, and none should be inferred from, anything in the present document.
To enhance acceptance of such a device by the medical community and regulatory authorities, it has been found desirable to focus attention upon certain operating characteristics of the Kulli device--particularly as they relate to peripheral but very important matters. Such matters include (1) manufacturing economics, and possible resulting variations in operation, (2) variations in skill of--and consequently variations in handling by--operating personnel, and resulting perceptions of medical appliances by operating personnel, and (3) potential misuse of the device, due for example to prevailing societal conditions.
It will now be understood that none of these considerations can properly be regarded as in the nature of a defect or limitation of Kulli's invention. Rather they are in the nature of areas in which that invention leaves room for further refinement.
None of these considerations is, in substance, a part of the prior art; instead they have been adduced through work leading to the present invention, and are regarded as at least in part components of the creative and innovative processes of making the present invention. Accordingly in this document these considerations will be detailed in a later section, not addressed to the prior art.
For reference purposes, however, the present section will now describe the overall procedure for inserting a cannula or the like--whether using the Kulli device or essentially any other cannula insertion set--as this procedure itself is a part of the prior art and will be of interest in later discussion of the present invention. Typically a doctor, nurse, paramedic or other medical staff person first locates a target blood vessel chosen for catheter insertion, and then pierces the patient's skin and blood-vessel wall--inserting the pointed end of the needle and a portion of the catheter (see FIG. 16 of Kulli).
Next the practitioner almost always deliberately permits a small quantity of the patient's blood to flow through the hollow needle--impelled by the patient's own blood pressure--so that the small quantity of blood can be seen at the rear of the needle. The blood which thus flows from the needle enters some sort of chamber that is part of the cannula insertion set, and which ordinarily is made of transparent material to afford a view of the interior and thus of the blood therein.
This practice of allowing some blood to flow into a viewing chamber is known in jargon of the medical field as "flashing", and the blood that enters the chamber is sometimes called the "flash" quantity. The flashing step has the purpose of confirming that the catheter is indeed inserted into the blood vessel.
In the instance of Kulli's invention, the chamber is the hollow handle into which the needle will later be retracted, and which thus serves double duty as a viewing chamber.
In other types of cannula insertion sets too the chamber may be a hollow handle, but may take other forms. In such other types of sets, the chamber is generally configured in one way or another to permit the flash blood to enter the chamber--but then to retain that blood.
To permit entry of that blood into the solid chamber, some provision must be made for escape of air that is initially in the chamber; on the other hand, retention of the blood once it has entered the chamber requires that the chamber be to some extent fluid sealed. These two seemingly contradictory requirements can be and are satisfied in a variety of ways, including careful placement of breather holes or tubes to permit air escape--and so accommodate the slow passage of blood into the chamber--while presenting a relatively long, high-impedance path to obstruct liquid flow out of the chamber.
More often modernly these requirements are met by providing--for instance at the rear end of the handle--a relatively large orifice that is closed by a selective filter to pass air somewhat readily, at least at the flow rates typically associated with blood flow into the chamber, but block passage of blood out of the chamber. As will be understood such purposes may be best served by for example a hydrophilic filter; such filters are sometimes used.
Once a desired flash quantity of blood is observed, as mentioned in the Kulli paten.sub.t the medical practitioner usually provides temporary stoppage of the blood flow by placing a finger or other hand portion upon the blood vessel to squeeze off the vessel. While maintaining this stoppage the practitioner carefully withdraws the needle, leaving the inserted end of the cannula or other appliance in place--and then secures an appropriate intravascular connecting tube, most typically a delivery tube, to the hub of the cannula etc.
Next the practitioner fixes the cannula or like appliance to the patient's body, usually employing a small piece of tape, and releases the manually applied closing pressure upon the vessel. Various liquids may then be introduced through the appliance into the patient's blood stream, the patient's blood pressure may be monitored, etc., all as well known.
Also part of the prior art are teachings of certain other Kulli patents, including U.S. Pat. No. 4,900,307, 4,904,242, 4,927,414 and 4,929,241--some of which disclose features related to deterrence of needle reuse, but in different contexts.
Important aspects of the technology used in the field of the invention are amenable to useful refinement.